Thursday 10 February 2000 05.31 EST
First published on Thursday 10 February 2000 05.31 EST

Geoffrey de Ste Croix, who has died aged 89, was one of the most distinguished and unusual ancient historians of his or any other generation. The vigour of his writing sprang from righteous indignation at the propertied classes' exploitation of the less fortunate: the way that fat cats have flourished at the expense of lean mice.

His first book, The Origins Of The Peloponnesian War (1972), also contained a political and military history of Sparta from archaic times to the end of the 5th century. For any serious student of the subject, there are two essential authors: Thucydides and de Ste Croix.

In 1981 he published the Isaac Deutscher Memorial Prize-winning The Class Struggle In The Ancient Greek World. Hailed for its contribution to Marxist theory, the author's Marxism recommended itself even to those unsympathetic to such views. He saw the exploitation of free and unfree labour by the propertied class as history's motive force, yet his was a class struggle in which there might be no awareness of class, and no overt struggle. The book covers 14 centuries, culminating in an explanation of the decline and fall of the Roman empire in the west.

Geoffrey, or "Croicks" as he mockingly referred to himself, did not start his academic life until he was 40. Born in Macao, he was educated at Clifton school in Bristol, and from 1926 to 1940 practised as a London solicitor. Wartime RAF service took him to Egypt, where he refreshed his knowledge of the ancient languages. He read ancient history at University College, London, and from 1950 to 1953 taught at the London School of Economics and Birkbeck College. He was then appointed fellow of New College, Oxford. There, for a quarter of a century, he taught Greek history.

His lectures were characterised by clarity of exposition. They expounded themes - slavery, finance, food supply - tackled by no other ancient historian in the Oxford of his day, and he gave classes on neglected subjects such as Greek science. He was proud of his contribution to the campaign to persuade the all-male Oxford colleges to to admit women. In the 1970s and 80s, he lectured in Cambridge, Poland - where, said a colleague "he harangued people about how their government misunderstood Marx" - Holland, France, Sweden and the US.

His scholarship was astonishing. When in 1985 his pupils presented him with Crux, his festschrift, the editors had to disregard more than half his interests to produce a coherent volume. His knowledge ranged from pre-colonial Greek exploits of the 8th century BC to the Arab conquests of the 7th century AD; biblical studies from Genesis by way of Job to Revelation, to say nothing of Marx and Marxism.

His early articles, The Character Of The Athenian Empire (1954/5) and Greek And Roman Accounting (1956), are classics; equally valuable are those on the persecution of the Christians, ancient maritime loans, and Roman religion. His Early Christian Attitudes To Property And Slavery (1975) provides an idea of the arguments of The Class Struggle In The Ancient Greek World.

The last 15 years of his life were spent on two large-scale books, Early Christian Attitudes To Women, Sex and Marriage, and Essays In Early Christian History. It became clear that neither would be completed, so he recast their most important parts in 12 essays, Radical Conclusions, to be published by Oxford University Press.

Powerfully built, with a great dome of a head, he competed at Wimbledon in 1929, and once defeated Fred Perry. His country walks might cover nine miles; on his return he would be refreshed by tea, served in two mugs, alternately replenished.

His scholarship was formidable, but he was not. Candid, straightforward, he had an austere charm and a sharp sense of humour. Lunch with Geoffrey at New College meant meeting him at 12.45 and talking throughout the afternoon; goodbye at 5.45 was perhaps the record. To the end he retained an urge to communicate, yet he always listened. One came away a better scholar, perhaps even a better human being. He was a great recommender and condemner - "you can't do better than to use a Pilot pen, but do make sure it's a V5"; "the crap written by that dreadful man Y". Yet he was always courteous, even to the character who, noticing that his leg was in plaster, remarked to him : "No more boppin', then".

He described himself as "an atheist, politely militant", and was increasingly militant with advancing years. St Paul replaced Plato as his "greatest enemy of the human race", and later that distinction went to Jahweh, the Old Testament Jehovah, whose cruelties never ceased to appal him. Yet he was always anxious not to offend sincere believers, and spoke with respect of the best Christian scholarship. He found little to quarrel with in liberation theology: Jesus was OK, his dad was appalling.

In his final years he bore infirmity with courage, including failing sight which must have been the most frustrating. "My memory has preceded me to the grave," he observed. He had once remarked that his doctor had advised him not to work more than 16 hours a day, and he worked to the very end.

An inspiring teacher, a magnificent scholar, one sensed his loathing of inhumanity, and his belief in democracy as a curb, however imperfect, on the oppressors. Few contributions to ancient history are read much longer than a generation. There are exceptions, such as Edward Gibbon and George Grote; Geoffrey, I suspect, will join that company.

He rarely spoke of earlier sorrows - an unhappy first marriage, and his daughter's suicide - but often of what brought him happiness: his love of music, his pride in his garden, the achievements of his family and, above all, his devotion to his wife Margaret, who survives him, as do his two sons.

Geoffrey Ernest Maurice de Ste Croix, historian, born February 8 1910, died February 5 2000